Prevention of scaling and encrustation



Jan-. 5,1926.- w 1,568,714

v c. E. BONINE PREVENTION OF SCALING AND ENCRUSTATION Filed August 26, 1925 na e as; 5, me I UNlTED STATES latent PATENT orrrca -CEA.RLES E. EONIN E, OF MELECSE PARK, PENNSYLVANIA, ASSIGNOR TO ANTISCAJLE CORPORATION, F IPHILADELPHIA, PENNSYLVANIA, A GQBPQRATIQN 01E DEM= WARE.

PREVENTION OF SCALING AND ENCEUSTATION Application filed August 26, 1925. Serial No. tiilfiw.

To all whom itmey concern: Be it known that l, CHAnLns E. Bormvn, a citizen of the United States, residing in Melrose Park, county of Montgomery, and 5 State of Pennsylvania, have invented new and useful Improvements in the Prevention of Scaling and Encrustation, of which the following is a specification. My invention relates to apparatus for the protection of metallic vsurfaces in contact with fluid against the formation of scaling and encrustation thereon.

The conditions under which scale and encrustation form upon metallic surfaces that are in contact with fluids are reasonably well known and it has been proposed heretofore to prevent such scaling and encrustation by the use of electric current that is either passed through the body of which the surface is to be protected against scaling oriencrustation or passed into'the fluid and withdrawn from the metallic body or vice versa. It has been roposed to protect metallic surfaces against encrustation and scaling by passing through the body of which the surface is to be protected an: electric current having a voltage so low that the normal or natural electrolytic corrosion will not be augmented or accelerated; To this end it has been proposedto so regulate the .poten tial difference between the points at which the source of current is connected to the body of which the surface is to be protected'that the potential difierence between those. points and the potential gradient along the surface between those two points.

will be so low-that the'electro'lytic corrosion of the surface will not be ap reciably augmented or accelerated beyon what would 40 that vis employed for the prevention or elimination of scaling or encrustation. It has been found that a potential gradient of one 'millhvolt or less per foot of distance between the points at which the terminals of the source of current are connected to the metallic body may safely be employed in connection with steam boilers compose of'ordinar boiler steel and using water of usual hard ness It has also been found that in the employment of electric current for the prevention of scale or encrustation on'metallic surfaces it is :not only necessaryto so regulate the voltage of the current in order normally occur in the absence of the current.

to prevent injury of the metallic surfaces but it is essential that the current flowing through the metallic body shall be of such value that the desired prevention or elimination of scaling or encrustation will be edected. It has been found that scaling and encrustation will be prevented if the amount of current flowing through the body is from. fifteen to several hundred milli-amperes per square foot of cross sectional area of metal in the case of steam boilers 'made of the; usual boiler steel. It has been proposed to protect a metallic surface by causing current at such a low voltage to flow therein by connecting the terminals of a thermo-couple to spaced points of the body of which the surface is to be protected but it is found that a flow of sullicient current to efiect the desired protection cannot be so produced, particularly in connection with large steam boilers or can only be produced with great difficulty. l ft is known that in regulating the voltage of the current account must be taken of the character of the metallic surface that is to be protected, the temperature thereof, and the continuity of the fluid that is in contact with the surface, as well as other surrounding circumstances, but ditliculty has not been experienced in the regulation of the voltage when a thermo-couple has been employed as a source of current.- lhe chief difliculty. in protecting metallic surfaces against scaling or encrustation is causing sufiicient current to flow at such low voltages throughthe body of which the surface is to be protected and this dificulty' is increased where the body is supported from a metallic structure as in the case where boilers are supported on steel beams, and where numerous and large pipes are connected to the boilers, and particularly where several boilers are connectedtogether in a single bank. Under these circumstances the current has considerable opportunity to be conducted away without performing its in tended function and it is dillicult to maintain a flow of'sufiocient current through the d body of which the surface is to be protected.

It is not. practicable to insulate joints of steam and water piping or to insulate supporting structures.

body of which the surface is to be protected 1 against scaling and encrusta'tion, such Sllfficient low of current being maintained at a voltage that is so low that normal electrolytic corrosion of the surface will not be accelerate-l or augmented beyond the electrolytic corrosion that would take place in the absence of the flow of a protective current. In the practice of my invention I provide a source of electric current that is capable of producing all the current that may be required to efiect the objects of my invention.

- referred to therein in which Fig. 1 shows diagrammatically apparatus embodying a simplified form of my invention, and

Fig. 2 shows diagratically a modified form of apparatus embodying my invention.

Understandin that the apparatus diagrammatically shown in the drawings that embodies my invention is to be considered as merely illustrative it will be seen that a steam boiler or other fluid container 1 which maybe of any construction or configuration is connected into the electrical circuit of a generator 2 that may be driven in any manner as by a motor 3 that may be of the valternating current type as shown or of any other type, the motor being supplied from a power circuit d. The generator is prefer- Zablyof the shunt wound type having a field coil 5. Que terminal of the generator is connected by the'electrical conductor 6 to one point of the body of which the surface is to be protected, the other terminal of the generator bein connected by the conductor 7 tea point 0 the body'of which the'surface is to be protected that is spaced from the point at which the conductor 6 is con nected to that body. The body of which the surface is to bev protected thus closes a complete circuit across the terminals of the generator. in order to meet-the requirements of satisfactory continuous operation, practical'considerations require that a generator shall produce current at at least five 'or'fsix volts: This voltage being far in excess of what may safely be impressed on such bodies as steam boilers, it is necessary to meet the practical requirement that the voltage of the generator be high by introducing into the circuit a large resistance that is usually lined and that is of sufficient capacity anemia to take the entire normal output of the gendesirable to make certain that the voltage impressed upon the body ofwhich the surface is to be protected shall be low enough to fall within the requirements herein set forth the next step being a determination of the suiiiciency of the current that 'will flow through the body of which the surface is to be protected. Thus after it has been determined that a proper voltage is being impressed upon the body of which the surface isto be protected, the next step is to determine Whether a suliicient current is flowing through the body. In this connection a convenient and efiective measure of the amount of current is the cross-sectional area of the body of which the surface is to be protected. The amount of current flowing through the body may readily be varied by the use of my invention from 15 milliamperes up to several hundred milli-amperes in order that encrustation and scaling may be prevented. For the final regulation of the current that flows through the body of which the surface'is to be protected 1 include in the circuit that contains that body a resistance R that is so constructed as to provide a high degree or adjustability. The amount of current that must flow in the cir cuit of the generator 2 will vary for the reasons above set forth, and the desired amount of current may be passed through it and the "Olta G drop or potential gradient across the body maintained at the desired value. 7

in order to protect a number of boilers B B B E the terminals of the generator 2 have respectively connected to them the main conductors 6 and 7, the main resistance R being connected in series in the conductor 6 ()ne of the main conductors, for example, the conductor 7 is directly connected to each ofthe boilers by connections per square foot of cross section of the body 8, 9, l0 and 11. Points on the boilers that are respectively spaced from the points of connection to the conductor 7 are connected through adjustable resistances 12, 13, 14' and 15 to the main conductor 6'. The boilers are thus connected in parallel between the main conductors 6 and 7 and care is taken that the circuits leading to the respective boilers shall have substantially equal resistances. To this end the boiler B is connected to the end of the conductor 6' bythe resistance 15 and'connected to that connection point of conductor 7 that is nearest to the generator 2. 4

For the purpose of testing the adjustment brought down to-a switch-board 16that is be understood that my invention is not lim- 'ited toisuch details but shall includesuch of thecircuit whereby a number 'ofboilers may be provided with current from asin le generator and in order to insure that in spite of various paths of leakage each unit is receiving a propersupply of current, each point of connectionto each boiler may be provided with a bridge' arm thatleads through the conductors 7 to any suitable-potentiometer I7. a

From the "foregoing will be apparent that I" have "provided apparatus whereby metallic bodies in contact with fluid may be provided with acurrent source whereby a sufficient flowof current may be maintained. through the body of which the surface 'is to be protected while the potential gradient.

of the current so flowing'may be maintained at such value that the normal electrolytic corrosion of'the surface/will not be 'aug-.

mented or accelerated.

While I have described in greatdetail apparatus embodying my invention it is to modifications and variations as fall'within tobe the hereunto appended] claims." In this connection it' will be-found that by proper regulation of the adjustable resistance the desired-amount of current can be assei through the body of'which the sur. ace is tial gradient of the current to exceed t e desired value. It has previousl been suggested that there may be a ifierence of potential between those points of a-body to which it is desired to connect the terminals.

of -.a source of electric current that is, due to electrolytic =or thermo-electric effects within the body or due to other causes.

Before connecting the" source of. the protective current to the selected points 'of= the body it should be ascertained,

' preferably by separate test, whether such a diiference of 1 potential exists and the source of protective current may then be so connected to the .body as to cause an additional flow of current therein in the same direction as .any current flowing therein-by reason of such difference of potential. Furthermore, it is to be understood that myinvention is not alone applicable to boilers but may be used in producing desired current at desired voltage in pipes and other kinds of containers and convey ors. An apparent modification of my invention consists in so designing the electrical conductors leading from the source of current to each body to be protected, with res e'ct to length and cross-sectional area that tiie resistance of such conductors may'take the place of or constitute the resistance R And, in the application of my invention to the protection of boilers comprising drums and connecting tubes the connections of the and encrustation, a source 0 protected without causing, the oten-.

- between a source of current to the variousparts of such a boiler should include a variable resistance for the regulation of the current entering the boiler at each point of the connection, as in the case of several boilers.

What I claim as new and desireto secure by Letters Patent of the United States is: I

.1; In apparatus for the protection of the surface of a metallic body against scaling.

and encrustation, a dynamo-electric .ma-

chine, electrical conductors respectively extending from the terminals of said machine to spaced points of the body of which the surface is to be protected and thereby formlng'a closed circuit, a resistance unit of relatively large capacity connected in the cir-- cuit so formed, and'an adjustable resistance also connected in the circuit so. formed,

whereby sufiicient cur-rent may be passed through the body to protect the surface thereof, at a suitably low' voltage.

2. In'apparatus for the protection of the surface of a metallic body a 'ainst scaling I 7 electric current capable of producing current at a relatively high voltage, electrical conductors respectively extending from the terminals of tors extending respectively from the terminals of said cource of current, a resistance unit of relatively large capacity connected in one of said conductors, electric connections 7 oint on each of said bodies and one of sai conductors, and adjustable resistances respectively connected between a point on each. of said bodies s aced from said first mentioned point an the other of said electrical conductors, whereb sufiicient current may be passed throng each of said bodies to protect the surface thereof at suitably low -voltage.

4. In ap aratus for the rotectio'n of the surfaces 0 a plurality o metallicv bodies a ainst scaling and 'encrustation, a source 0 current capable of producing acurrent at a relatively high volta e, electric conductors extending respectively from the terminals of said source of current, aresistance unit of .relativeiy large'capacit connected inone of said conductors, etectric connections between apoint on each of said bodies and one of said conductors, and adjustable resistances respectively connected between a point on each of said bodies. 5 aced from said first mentioned point and the other of said electrical conductors, the length of conductor by which each body is connected to the terminals of said source being substantially equal, whereby sufficient current may be passed through each of said bodies to protect the surface thereof at suitably low voltage.

5. In apparatus for the protection of the surface of a metallic body against scaling and encrustation, a dynamo-electric machine, electrical conductors respectively extending from the terminals of said machine to spaced points of the body of which the surface is to be protected and thereby forming a closed circuit, a resistance unit of sufficient capacity to withstand the normal output of said dynamo-electric machine and connected in the circuit so formed, and an adjustable resistance also connected in the circuit so formed, whereby sufficient current may be passed through the body to protect the surface thereof, at a suitably low voltage.

6. In ap aratus for-the protection of the surfaces or a plurality of metallic bodies a ainst scaling and encrustation, a source 0 current capable of producing a current at a relatively high voltage, electric conduetors extending respectively from the terminals of said source of current, 'a resistance unit of sufiicient capacity to withstand the normal output of said source connected point on each of said bodies spaced from said first mentioned point and the other of said electrical conductors, whereby sufiicient current may be. passed through each of said bodies to protect the surface thereof at suitably low voltage.

7. In apparatus for the protection of the surfaces of a metallic body against scaling and encrustation a source of electric current capable of producing several amperes of current and of relatively high voltage, an electric circuit of relatively high resistance connecting the terminals of said source of currents with spaced points upon the body to be protected and thereby forming a closed circuit, and an adjustable resistance also connected in said circuits'so formed; whereby sutgcient current may be passed through the ody to effect surface thereof at suitably ow voltage.

In testimony whereof, I have signed my name to this specificatiom' CHARLES E. BONINE.

protection of the 

